The rule of thirds is a technique that can be used in your photography to improve the composition of your photos. Using the rule of thirds means that the subject isn't centered in the image, it also means that the main focus points of the image meet up along the lines, for example in the image below the horizon approximately meets the top line of the grid and the island in the distance meets up with the cross of the lines in the corner and the boat meets up with the grid on either end of the boat, this use of the rule of thirds create an interesting composition in the photo.